From the viewpoint of simple and inexpensive image production, an inkjet recording method has been used in a variety of printing fields. As the inkjet recording method, there is an actinic radiation-curable inkjet method in which droplets of actinic radiation-curable ink are attached on a recording medium and then the droplets of the ink attached on the recording medium is cured by irradiation with actinic radiation to form an image.
In relation to an inkjet ink to be used in the actinic radiation-curable inkjet method, there is known a technique of allowing an actinic radiation-curable inkjet ink to contain a gelling agent in order to prevent the ink from being unnecessarily mixed together due to wet spread of the ink after the ink is attached on a recording medium and before the ink is cured. In this technique, the gelling agent enables sol-gel phase transition through a temperature change, and thus the ink undergoes gelation after being attached on a recording medium and before being irradiated with actinic radiation so that ink mixing (color mixing) can be prevented.
When a usual inkjet ink is used for recording on a recording medium high in optical transparency, such as one to be used in soft packaging, the recording medium is transparent, thus cannot achieve the same contrast as that in recording on a blank recording medium, cannot sometimes achieve brilliant color production, and has difficulty in providing visible representation.
Therefore, when an inkjet ink is used for recording on a recording medium high in optical transparency, a known technique of enhancing visibility is adopted in which an image is subjected to white top coating or primer coating with an white ink having masking ability.
Titanium oxide high in masking ability is known as a pigment to be used in the white ink. For example, in PTL 1, an actinic radiation-curable inkjet ink containing titanium oxide high in masking ability as a white ink pigment is used.